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A Manhattan ad executive who went out to smoke on the balcony of her 17th-floor apartment while on a first date plunged to her death early Thursday morning when she sat on the railing and it gave way. Tracie Strahan reports. (Published Thursday, Aug 1, 2013)

Updated at 7:08 AM EDT on Friday, Aug 2, 2013

A Manhattan ad executive who went out to smoke on the balcony of her 17th-floor apartment while on a first date plunged to her death early Thursday morning when she sat on the railing and it gave way, according to police sources.

Sources told NBC 4 New York that Jennifer Rosoff, 35, and her date were on the balcony at about 12:30 a.m. and when she sat on the railing's corner, it broke and she plunged to the ground, hitting scaffolding on the way down.

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Her date told investigators he heard two pops before the railing gave way.

Witnesses reported seeing a screaming man, believed to be Rosoff's date, running from the building at 400 E. 57th St in Sutton Place. Police spoke to him and cleared him of any wrongdoing.

A source on the scene provided a description of the railing, which appeared to be metal, and was bent and twisted, with a cigarette lighter still sitting nearby.

The Buildings Department is investigating.

Only the higher-floor corner apartments in the gray brick building have balconies, and the Buildings Department issued a partial vacate order for them Thursday.

A neighbor of Rosoff on the 17th floor, who did not want to give his name, told NBC 4 New York his landlord had sent the superintendent and an inspector to examine his balcony two or three months ago.

"They just asked to peek at it, and I just assumed they were only talking about the surface of it, because that's what they had worked on," he said.

A mother who also lives in the building said she was worried for her daughter's safety after the tragedy.

"I hope they're checking a lot more than the terraces," she said. "Everything should be checked."

The landlord, Stonehenge Management, LLC, did not immediately respond to requests for comment.

Rosoff, who had worked at The New Yorker and Lucky Magazine, was director of sales at TripleLift, an advertising company on Fifth Avenue. CEO Eric Berry told NBC 4 New York the staff was struggling Thursday after learning of her death.

"She was a well-loved and highly respected member of our team," Berry said in a statement. "The entire company is distraught by the loss of Ms. Rosoff -- she will be deeply missed."

Samantha Massa, an acquaintance of Rosoff, told NBC 4 New York said "she was ambitious, she had a great career."

Rosoff's family said funeral services were scheduled for this weekend.